A disk laser, particularly a thin disk laser, is a laser whose active gain medium is a thin crystal disk. For example, a ytterbium (Yb) doped yttrium aluminum garnet (YAG) disk laser can include a Yb:YAG or Yb:LuAG crystal disk with a thickness of about 100-200 μm. Cooling is typically required for the thin crystal disk. A metal disk, e.g., made of cooper with a thermal conductivity of about 400 W/(m·K), can be used to build a heat sink to provide the cooling for the thin crystal disk during operation of the disk laser. In some cases, a high-power disk laser can have much higher cooling requirement than what a metal disk can provide. Diamond has a higher thermal conductivity, e.g., about 2000 W/(m·K), than cooper, and a diamond disk can be used to provide the cooling for the high-power disk laser. However, due to dissimilar thermal expansion coefficients between the diamond and the active gain medium of the crystal disk, the diamond disk is hard to be thermally expansion matched to the crystal disk. The diamond disk is also expensive to be used for disk lasers.